EPC Memory

EPC Memory

epc-memory/" class="glossary-term-link" data-term="EPC Memory" data-definition="Writable tag memory for item identity." data-category="Data & Encoding">EPC Memory (Memory Bank 01) is the primary data storage area on an EPC Gen2 RFID tag. It holds the Electronic Product Code — the unique identifier that links a physical object to its digital record in enterprise systems. EPC Memory is the memory bank that readers access most frequently during inventory operations, and its contents define the item's identity throughout the supply chain.

Memory Layout

The EPC memory bank contains several fields:

The most common configuration is a 96-bit EPC, yielding a total EPC memory bank size of 128 bits (16 CRC + 16 PC + 96 EPC). Some applications use extended EPCs of 128, 256, or even 496 bits for larger identifier spaces.

Encoding Schemes

The EPC stored in this memory bank can follow multiple encoding schemes defined by the GS1 Tag Data Standard:

• SGTIN: Serialised trade items (retail, pharma)
• SSCC: Serial Shipping Container Codes (logistics)
• GRAI: Returnable asset identifiers
• GIAI: Individual asset identifiers
• SGLN: Location identifiers
• GDTI: Document identifiers

The first 8 bits (header) of the EPC field identify which encoding scheme is in use, allowing readers and middleware to parse the remaining bits correctly.

Writing EPC Memory

EPC Memory is writable — this is what enables commissioning workflows where blank tags are encoded at the point of use. A printer-encoder or encoding station writes the desired EPC value using the Gen2 Write command. The write operation targets individual 16-bit words, with each word write taking approximately 20 ms.

For faster encoding, the Block Write command can write multiple words in a single transaction. This is particularly important in high-throughput source tagging lines where encoding speed directly impacts production throughput.

Access Protection

EPC Memory can be protected using the Access Password mechanism. When an access password is set and the memory bank is locked, any subsequent write attempt requires the reader to first authenticate with the correct 32-bit password. This prevents unauthorised overwriting of tag identity — a critical concern in retail loss prevention and pharmaceutical track-and-trace.

For maximum security, the Permalock feature can permanently prevent writes to specific memory words, ensuring that the EPC can never be altered after initial encoding.

EPC Memory vs. Other Banks

Understanding the four-bank architecture is essential. TID Memory provides physical chip identity; EPC Memory provides logical item identity; User Memory provides supplementary application data; and Reserved Memory stores passwords. Each serves a distinct role in the overall data model.